1. Field of the Invention
The invention relates to an ignition coil; in particular, the invention relates to an ignition coil with terminals that can be precisely positioned during assembly.
2. Description of the Related Art
An ignition coil ignites combustible gas by high voltage. Referring to FIG. 1a, a conventional ignition coil 10 includes a casing 20, a bobbin 30, a primary coil 80 (shown in FIG. 1b), two secondary coils 90 (shown in FIG. 1b), a circuit (not shown) and a bar core 70. The casing 20 is made of plastic.
The bobbin 30 is disposed inside the casing 20, as shown in FIG. 1b. The bobbin 30 is provided with a primary portion 50 and two secondary portions 60. The primary portion 50 separates the secondary portions 60 by partitions (not labeled).
The bobbin 30 further includes two terminals 51 and four pins 62. The primary portion 50 is surrounded by the primary coil 80 as shown in FIG. 1b. The primary coil 80 is electrically connected to the terminals 51. The secondary portion 60 is surrounded by the secondary coil 90 as shown in FIG. 1b. One end of the secondary coil 90 attaches to one of the pins 62, and the other end of the secondary coil 90 attaches to the other pin 62 by solder.
The bar core 70 penetrates the bobbin 30 to provide a magnetic route. The circuit converts a DC voltage to a triggering-voltage signal. The triggering-voltage signal inputs to the primary coil 80. The D.C. voltage is converted to a high voltage by the voltage conversion of the primary coil 80 and the secondary coil 90. The high voltage ignites the combustible gas through the pins 62 in a tip-discharging manner.
The casing 20 is filled with a resin such as an epoxy resin to prevent high voltage generated by the coil from leaking out of the casing 20 causing dielectric breakdown.
FIG. 1b is a schematic view of the assembled ignition coil 10 in FIG. 1a. During assembly, the pins 62 must pass through holes 25, formed in the casing 20, to expose their tips. As a result, the filled resin is able to leak out of the casing 20 through the holes 25 with diameter is larger than that of the pin 62. Accordingly, a design in which the diameter of the hole 25 is smaller than the diameter of the pin 62 is provided. However, in such a design, a wire 40, attached to the pin 62, is easily broken when the pin 62 passes through the hole 25, because the diameter of the pin 62 is larger than that of the hole 25, hence, the pin 62 is easily squeezed out of the hole and then the wire 40 may be broken by the movement of the pin 62 as shown in FIG. 1c. 
Therefore, it is desirable to develop an ignition coil that can prevent attached wire breakage and resin leakage during assembly.